In school I was always taught that temperature is proportional to the average kinetic energy of the individual particles in that object. However, I recently encountered a brief statement in a 1999 issue of The Physics Teacher that this is only really the case for ideal gases. Here is the quote from PT: "Quantum effects can lock out certain energy levels, thus prohibiting energy exchanges between particles. For instance, at room temperature, the average kinetic energy of the electrons in a metal is of the order of several eV or tens of thousands K." -PT 1999 Survey of High School Physics Texts (authored by the PT editorial staff) How correct is this? How wrong is it to generally say that temperature is proportional to the average kinetic energy of the individual particles? What would be a good way to think about/define temperature? Also, if metals have all that KE, why don't they feel incredibly hot? Why doesn't energy tend to flow out of a metal rapidly and into the metal's less energetic surroundings? Why doesn't the metal either A) radiate this energy away via electromagnetic waves, or B) pass this energy to surroundings/objects that are in thermal contact with the metal?